Demolition devices have commonly utilized compressed air and reciprocating pistons, as in drills or jack hammers used to drill holes in rock, concrete or the like, as for the introduction of an explosive, or blades or the like reciprocated by jack hammers or the like to remove somewhat softer material, such as asphalt paving. Similarly, explosives have been used in the production of sound waves, as for geophysical exploration, by placing in holes drilled in the earth, sometimes to substantial depths, as by small drilling rigs. Devices which are operated by compressed air and used to break up concrete or rocks, involve large amounts of energy and produce vibration and shaking of not only the device itself but also the supporting equipment, as well as an individual operator. Such supporting equipment normally sustains considerable damage, with the result that the cost of maintenance is very high. When vibration absorbing devices have been added to the equipment, such as heavy coil springs, the cost of the same has been unduly high. Also, while the supply of compressed air to the drilling equipment, through hoses, has not involved a particular problem, controls for the equipment, when extended thereto, have involved considerable problems.
Impact devices adapted to drive nails and the like and involving a ram driven by one or two rotating flywheels to impact a series of nails in succession, are represented generally by U.S. Pat. Nos. 4,042,036; 4,121,745; 4,129,240; 4,189,090; 4,204,622; 4,293,493; 4,298,072 and 4,323,127. In each of these devices, which are designed to be hand held, the force required to drive the nail requires that the flywheel or flywheels continue in engagement with the ram, after the nail has been impacted by the ram or by a nail driving tool attached to the ram and until shortly before the nail is completely driven. Also, in order to develop sufficient force to drive the nail, a maximum of kinetic energy must be extracted from the flywheel or flywheels, so that the time required to accelerate the flywheel or flywheels back up to speed limits the time within which impacts against successive nails may be repeated. While the driving of nails produces a certain amount of vibration, the effect is fairly limited, since the number of foot pounds required to drive a nail is on a low order or magnitude, such as 125 foot pounds. However, when a ram is utilized to hit a chisel, for instance, for breaking up rocks of a size which require hoisting equipment to move them and blows in excess of one thousand foot pounds to break them, the reaction produced, if the flywheels continue to engage the ram, after a chisel, for instance, has been hit by the ram, has been found to be equivalent to the vibration produced by reciprocating air driven devices of the jack hammer and air drill types.
Certain features of the impact device of my copending application Ser. No. 407,089 filed Aug. 11, 1982, however, have been found to be useful on heavy duty devices, particularly the discovery that a ram having sides engageable by flywheels for driving purposes, which are formed of a suitable plastic, such as polyurethane, in which a woven natural fiber such as long fiber cotton, is embedded, shows a surprising resistance to wear which has been found also to be present in heavy duty devices of the character described herein.
Among the objects of this invention are to provide a heavy duty device which produces forces in excess of one thousand foot pounds and particularly adapted to be used for demolition, percussion and the like purposes; to provide such a device which is comparatively free from vibration, particularly when compared with the air driven impact devices; to provide such a device which is capable of producing forces of a high magnitude for demolition purposes, such as breaking up reinforced concrete, large rocks and the like; to provide such a device which is readily mountable on a vehicle, so that it may be moved from one place to another and may be readily shifted in position by such a vehicle; to provide such a device which may be effectively controlled and which produces blows, as by a ram, of high magnitude and may be repeated in fractions of a second; to provide such a device which permits a tool, such as a chisel, to be readily replaced when desired; to provide such a device in which a blow against a tool, as by a ram, may be absorbed when the device is accidentally fired without an adequate article or the like in the way of the tool, but the energy of the tool is at least partially absorbed, so that destruction of parts associated with the tool is avoided; to provide such a device which can be used for percussion purposes, such as striking the earth to produce shock waves which are detectable for seismic purposes; to provide such a device which may strike repetitive blows against a tool or the like, which, in turn, strikes an object such as the earth or a rock or the like; to provide such a device which may utilize a special construction in order to maintain the flywheels in exact alignment with the ram, so that neither of the flywheels tends to twist and thereby produce a greater driving effect by one flywheel than by the other; to provide such a device which is particularly adapted to strike a tool, such as a chisel, which requires repeated blows against an object, such as a rock or a reinforced concrete slab, before the tool penetrates the object or shatters portions of the object; to provide such a device which produces a minimum of vibration during use and thereby minimizes damage to a vehicle or other support for the device; to provide such a device in which a relatively heavy spring is placed in a position to absorb the energy of the ram on its return or upward stroke and then return energy to the ram, thereby starting the ram on its downward stroke so that the ram will be moving when engaged by the rotating flywheels; to provide such a device in which the position of the upper end of the ram on its return or upward stroke may be utilized in order to control the movement of at least one flywheel inwardly toward the ram; to provide such a device in which the position of the lower end of the ram on its downward stroke may be utilized to cause the flywheels to withdraw from the ram as soon as the upper end of the ram has moved beyond the flywheels; to provide such a device in which the ram may be protected against accelerated downward movement at a time when the tool to be struck by the ram is not engaging the work which the tool is intended to strike, in order to eliminate abortive blows of the ram which would need to be absorbed by the housing or supporting structure; and to provide such a device which is readily controlled and is efficient and effective in operation.